Project Summary/Abstract Uveal melanoma is the most common intraocular tumor malignancy in adults, however no effective therapies are available for metastatic uveal melanoma patients. This results in an average survival of 2-8 months. Constitutively active mutations in G?q and G?11 have been reported in up to 83% of uveal melanomas, however no inhibitors are available for constitutively active G?q or G?11. The purpose of this study is to (1) understand the role of palmitoylation in localization and signaling of constitutively active G?q/11 in uveal melanoma cells and (2) to determine if targeting palmitoylation of G?q/11 can prevent G?q/11-dependent signaling and growth. Using immunofluorescence microscopy and cellular fractionation of HEK 293 cells and uveal melanoma cells, constitutively active G?qQ209L shows decreased localization at membranes compared to wild type G?q, suggesting increased turnover of attached palmitate. Moreover, a palmitoylation-deficient G?qQ209L displays a complete loss of plasma membrane localization and an inability to signal as measured by YAP translocation into the nucleus, TEAD- dependent luciferase activity, and ERK phosphorylation. The loss of signaling in the palmitoylation-deficient mutant may result from its inability to localize to membranes. These studies demonstrate that palmitoylation of mutationally activated G?q/11 is required for its signaling functions, providing a novel target to consider for inhibition of activated G?q/11 in uveal melanoma.